That's just it - we can never know for certain, but given the evidence we do have, we can consider some possibilities as more likely than others.
The reason I don't believe the PF was confronted with a wildly divergent display from his colleague in the LHS is in part because I know that's not how the system works, and also because at no point is a discrepancy between the two PFDs and ISIS commented on by any of the crew - including the Captain, who after he arrived had a clear view of all three.
The reason I believe the pitch was commanded by the PF and not the automatics is because the DFDR traces of the stick input and pitch attitude tally almost perfectly up until the point of stall.
The reason I believe the displays were consistent with having lost speed information is the PNF's call at 02:10:15.9. ECAM is for systems-level troubleshooting, not maintaining or regaining control. The PFDs should be enough for that.
Lest this be perceived as a defence of Airbus, I believe they should have been a lot more pro-active about replacing the Thales AA pitot tubes than they were, and should have been more forceful in pushing for high-altitude manual handling and stall training. I think Air France should have mandated all three flight crew to be present on long-haul ITCZ crossings until the problem was fixed. I also think their CRM training was in dire need of overhaul.